Reply to “Comment on ‘A Vertical Exposure of the 1999 Surface Rupture of the Chelungpu Fault at Wufeng, Western Taiwan: Structural and Paleoseismic Implications for an Active Thrust Fault,’ by Jian-Cheng Lee, Yue-Gau Chen, Kerry Sieh, Karl Mueller, Wen-Shan Chen, Hao-Tsu Chu, Yu-Chang Chan, Charles Rubin, and Robert Yeats,” by Yuan-Hsi Lee, Shih-Ting Lu, Tung-Sheng Shih, and Wei-Yu Wu

We welcome Y. H. Lee et al.'s interest in our article (Lee et al., 2001). We thank them for their comment, which provides a further opportunity for discussing the quantification of the slip amounts including horizontal and vertical components and the fault geometry for an earthquake thrust scarp in Wufeng, western Taiwan, during the 1999 M 7.6 earthquake. In their comment, Y. H. Lee et al. used restoration of deformed concrete fence across the 1999 scarp to estimate the slip vector of the main fault. The estimated slip amount, especially the horizontal component, is different (significantly less) from our results presented in the 2001 BSSA article. They then applied an “area-balance” technique to compare their results with ours. They showed that their area-balance method favored their estimates including the slip amounts and the fault dip angle. They concluded that their estimated slip amounts are more reasonable than ours. The fundamental questions in this issue, in our opinions, include the actual amounts of deformation (slip) and the associated deformation processes, as well as the limitation and uncertainty of the applied techniques on an earthquake-formed thrust scarp. Hereafter we attempt to answer these questions and clarify the related problems